Thermosetting composition, resin sheet, metal foil with resin, metal-clad laminate, and printed wiring board

ABSTRACT

A thermosetting composition according to the present disclosure contains: an ethylene-propylene-diene copolymer as Component (A); and an inorganic filler, as Component (B), surface-treated with a surface treatment agent having a polymerizable unsaturated bond.

TECHNICAL FIELD

The present disclosure generally relates to a thermosetting composition,a resin sheet, a sheet of metal foil with resin, a metal-clad laminate,and a printed wiring board, and more particularly relates to athermosetting composition, a resin sheet including a dried product orsemi-cured product of the thermosetting composition, a sheet of metalfoil with resin having a resin layer including a semi-cured product ofthe thermosetting composition, a metal-clad laminate with an insulatinglayer including a cured product of the thermosetting composition, and aprinted wiring board with an insulating layer including a cured productof the thermosetting composition.

BACKGROUND ART

Various techniques for conveying information at even higher speeds havebeen developed continuously. To obtain a printed wiring board with thecapability of processing such high-speed signals for such purposes,there has been an increasing demand for further lowering the dielectricconstant and dielectric loss tangent of an insulating layer of theprinted wiring board.

For example, Patent Literature 1 discloses, as a material for aninsulating layer of a printed wiring board, a thermosetting adhesivecomposition containing, at a predetermined ratio: a vinyl compoundhaving a polyphenylene ether skeleton; a maleimide resin having two ormore maleimide groups; and an elastomer composed mainly of apolyphenylene skeleton and serving as a copolymer of a polyolefin blockand a polystyrene block. Patent Literature 1 describes that thisthermosetting adhesive composition has a low dielectric constant and alow dielectric loss tangent, exhibits high adhesive strength to an LCPfilm and copper foil, and has high heat resistance (see, for example,paragraph [0036] of Patent Literature 1).

CITATION LIST Patent Literature

Patent Literature 1: WO 2016/117554 A1

SUMMARY OF INVENTION

It is therefore an object of the present disclosure to provide: athermosetting composition, of which a cured product is able to have alow dielectric constant, a low dielectric loss tangent, high heatresistance, and excellent adhesiveness to a resin; a resin sheetincluding a dried product or semi-cured product of the thermosettingcomposition; a sheet of metal foil with resin having a resin layerincluding a semi-cured product of the thermosetting composition; ametal-clad laminate with an insulating layer including a cured productof the thermosetting composition; and a printed wiring board with aninsulating layer including a cured product of the thermosettingcomposition.

A thermosetting composition according to an aspect of the presentdisclosure contains: an ethylene-propylene-diene copolymer as Component(A); and an inorganic filler, as Component (B), surface-treated with asurface treatment agent having a polymerizable unsaturated bond.

A resin sheet according to another aspect of the present disclosureincludes a dried product or semi-cured product of the thermosettingcomposition.

A sheet of metal foil with resin according to still another aspect ofthe present disclosure includes: a sheet of metal foil; and a resinlayer laid on top of the sheet of metal foil. The resin layer includes adried product or semi-cured product of the thermosetting composition.

A metal-clad laminate according to still another aspect of the presentdisclosure includes: an insulating layer; and a sheet of metal foil. Theinsulating layer includes a cured product of the thermosettingcomposition.

A printed wiring board according to yet another aspect of the presentdisclosure includes: an insulating layer; and conductor wiring. Theinsulating layer includes a cured product of the thermosettingcomposition.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a schematic representation illustrating an exemplary sheet ofmetal foil with resin according to an exemplary embodiment of thepresent disclosure;

FIG. 1B is a schematic representation illustrating another exemplarysheet of metal foil with resin according to the exemplary embodiment ofthe present disclosure;

FIG. 2A is a schematic representation illustrating an exemplarymetal-clad laminate according to the exemplary embodiment of the presentdisclosure;

FIG. 2B is a schematic representation illustrating another exemplarymetal-clad laminate according to the exemplary embodiment of the presentdisclosure;

FIG. 2C is a schematic representation illustrating still anotherexemplary metal-clad laminate according to the exemplary embodiment ofthe present disclosure;

FIG. 2D is a schematic representation illustrating yet another exemplarymetal-clad laminate according to the exemplary embodiment of the presentdisclosure;

FIG. 3A is a schematic representation illustrating an exemplary printedwiring board according to the exemplary embodiment of the presentdisclosure;

FIG. 3B is a schematic representation illustrating another exemplaryprinted wiring board according to the exemplary embodiment of thepresent disclosure;

FIG. 3C is a schematic representation illustrating still anotherexemplary printed wiring board according to the exemplary embodiment ofthe present disclosure; and

FIG. 3D is a schematic representation illustrating yet another exemplaryprinted wiring board according to the exemplary embodiment of thepresent disclosure.

DESCRIPTION OF EMBODIMENTS

An exemplary embodiment of the present disclosure will be describedbelow.

When used in applications demanding high reliability such as onboardapplications, the printed wiring board is required to have even higherperformance. With this regard, the heat resistance of the thermosettingadhesive composition disclosed in WO 2016/117554 A1 and its adhesivenessto resin are not high enough to achieve this.

Thus, the present inventors carried out extensive research anddevelopment to provide a thermosetting composition, of which a curedproduct is able to have a low dielectric constant, a low dielectric losstangent, high heat resistance, and excellent adhesiveness to a resin,thereby acquiring an idea that forms the basis of the exemplaryembodiment to be described below.

1. Overview

A thermosetting composition according to an exemplary embodiment(hereinafter referred to as “Composition (X)”) contains: anethylene-propylene-diene copolymer as Component (A); and an inorganicfiller, as Component (B), surface-treated with a surface treatment agenthaving a polymerizable unsaturated bond. A cured product of thisComposition (X) is able to have a low dielectric constant, a lowdielectric loss tangent, high heat resistance, and excellentadhesiveness to metals and resins. Therefore, the Composition (X) issuitably applicable as a material for making the insulating layer of ametal-clad laminate and a printed wiring board. In that case, theComposition (X) is able to give good radio frequency characteristics andhigh reliability to the printed wiring board.

This embodiment achieves the advantage of providing: a thermosettingcomposition, of which a cured product is able to have a low dielectricconstant, a low dielectric loss tangent, high heat resistance, andexcellent adhesiveness to a resin; a resin sheet including a driedproduct or semi-cured product of the thermosetting composition; a sheetof metal foil with resin having a resin layer including a semi-curedproduct of the thermosetting composition; a metal-clad laminate with aninsulating layer including a cured product of the thermosettingcomposition; and a printed wiring board with an insulating layerincluding a cured product of the thermosetting composition.

2. Composition (X)

Next, the components of the Composition (X) will be described in detail.

The ethylene-propylene-diene copolymer as Component (A) is generallyalso called “EPDM (ethylene-propylene-diene monomer) rubber.”

The ethylene-propylene-diene copolymer as Component (A) has a structuralunit derived from ethylene (hereinafter referred to as an “ethyleneunit”), a structural unit derived from propylene (hereinafter referredto as a “propylene unit”), and a structural unit derived from diene(hereinafter referred to as a “diene unit”). The diene unit suitablyincludes a structural unit derived from 5-ethylidene-2-norbornene(hereinafter simply referred to as “5-ethylidene-2-norbornene”). That isto say, the ethylene-propylene-diene copolymer as Component (A) suitablyincludes the component expressed by the following Formula (1), where n,m, and 1 are natural numbers indicating the numbers of structural unitsin Formula (1). That is to say, Formula (1) indicates that one moleculeof the copolymer as Component (A) includes n ethylene units, m propyleneunits, and 1 5-ethylidene-2-norbornene units as diene units. The5-ethylidene-2-norbornene unit as a diene unit contributes to increasingthe curing reaction rate of the Composition (X), thus shortening theamount of time it takes to cure the Composition (X). Note that thestructural unit included in the diene unit is not necessarily the5-ethylidene-2-norbornene unit. Alternatively, the diene unit may alsoinclude at least one structural unit selected from the group consistingof the 5-ethylidene-2-norbornene unit, a dicyclopentadiene unit, and a1,4-hexadiene unit.

The percentage by mass of the diene unit to the entireethylene-propylene-diene copolymer as Component (A) is suitably equal toor greater than 3% by mass, which would contribute to improving the heatresistance of the cured product. The percentage of the diene unit moresuitably falls within a range from 3% by mass to 15% by mass.

The percentage by mass of the ethylene unit to the entireethylene-propylene-diene copolymer as Component (A) is suitably equal toor greater than 50% by mass. This facilitates forming the Composition(X) into a sheet shape. The percentage of the ethylene unit moresuitably falls within a range from 50% by mass to 75% by mass.

The Mooney viscosity ML (1+4) 100° C., defined by JIS K6300-1:2013, ofthe ethylene-propylene-diene copolymer as Component (A) is suitablyequal to or greater than 10. This also facilitates forming theComposition (X) into a sheet shape. The Mooney viscosity ML (1+4) 125°C., defined by JIS K6300-1:2013, of the ethylene-propylene-dienecopolymer as Component (A) is more suitably equal to or less than 80.

Note that the larger the molecular weight of theethylene-propylene-diene copolymer as Component (A) is, the higher theMooney viscosity of the ethylene-propylene-diene copolymer as Component(A) is. Thus, the Mooney viscosity of the ethylene-propylene-dienecopolymer as Component (A) is controllable by adjusting the molecularweights of the molecules included in the ethylene-propylene-dienecopolymer as Component (A), or by blending molecules with differentmolecular weights with the ethylene-propylene-diene copolymer asComponent (A) and adjusting the blending ratio thereof, or by turningthe molecules included in the ethylene-propylene-diene copolymer asComponent (A) into a branched structure.

The Composition (X) may contain not only the ethylene-propylene-dienecopolymer as Component (A) but also an organic compound having apolymerizable unsaturated group as Component (C). The polymerizableunsaturated group includes at least one group selected from the groupconsisting of a vinyl group, an allyl group, a methallyl group, a styrylgroup, a meth(acrylic) group, and a maleimide group. When theComposition (X) contains an organic compound as Component (C), thephysical properties of the Composition (X) and a cured product thereofare controllable by selecting appropriate components included in theorganic compound as Component (C). For example, if the organic compoundas Component (C) contains a monofunctional compound including a singlepolymerizable unsaturated group per molecule, then the monofunctionalcompound is able to reduce the melt viscosity of the Composition (X) toimprove the formability. On the other hand, if the organic compound asComponent (C) contains a polyfunctional compound including a pluralityof polymerizable unsaturated groups per molecule, then thepolyfunctional compound is able to increase the crosslink density of thecured product. Thus, the polyfunctional compound contributes toincreasing the toughness, the glass transition temperature, andtherefore, the heat resistance of the cured product, decreasing thelinear expansion coefficient thereof, and increasing the degree ofadhesiveness thereof.

If the organic compound as Component (C) contains a polyfunctionalcompound with a plurality of polymerizable unsaturated groups, then thepolyfunctional compound includes at least one compound selected from thegroup consisting of: the compound expressed by the following ChemicalFormula (2); bismaleimide; divinylbenzene; trivinylcyclohexane; triallylisocyanurate (TAIC); dicyclopentadiene dimethanol dimethacrylate, andnonanediol dimethacrylate. The polyfunctional compound may includeeither the compound expressed by the following Formula (2) orbismaleimide, or both. In Formula (2), R is a single-bond organic groupor a divalent organic group, and the organic group may be a hydrocarbongroup, for example. Examples of the compounds expressed by the followingFormula (2) include DD-1 manufactured by Shikoku Chemicals Corporation.If the polyfunctional compound includes bismaleimide, the bismaleimideincludes at least one compound selected from the group consisting of:4,4′-diphenylmethane bismaleimide; m-phenylene bismaleimide; bisphenol Adiphenyl ether bismaleimide;3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethane bismaleimide;4-methyl-1,3-phenylene bismaleimide; 1,6-bismaleimide-(2,2,4-trimethyl)hexane; and BMI-689, which is the name of a product manufactured byDESIGNER MOLECULES.

If the Composition (X) contains the organic compound as Component (C),then the content of the organic compound as Component (C) suitably fallswithin a range from 1 part by mass to 100 parts by mass, and moresuitably falls within a range from 10 part by mass to 100 parts by mass,relative to 100 parts by mass of the ethylene-propylene-diene copolymeras Component (A). When the content of the organic compound as Component(C) is equal to or greater than 1 part by mass, the organic compound asComponent (C) contributes particularly effectively to improving thephysical properties of the Composition (X) or a cured product thereof.For example, when the organic compound (C) includes a polyfunctionalcompound and the content of the polyfunctional compound is equal to orgreater than 1 part by mass, the polyfunctional compound contributes toincreasing the toughness, the glass transition temperature, andtherefore, the heat resistance of the cured product, decreasing thelinear expansion coefficient thereof, and increasing the degree ofadhesiveness thereof. In addition, when the content of the organiccompound as Component (C) is equal to or less than 100 parts by mass, anincrease in the dielectric constant of the cured product is reducible.

The inorganic filler as Component (B) may contain at least one materialselected from the group consisting of silica, alumina, talc, aluminumhydroxide, magnesium hydroxide, titanium oxide, mica, aluminum borate,barium sulfate, boron nitride, forsterite, zinc oxide, magnesium oxide,and calcium carbonate.

As described above, the inorganic filler as Component (B) has beensubjected to surface treatment using a surface treatment agent having apolymerizable unsaturated bond. The polymerizable unsaturated bondincludes at least one group selected from the group consisting of avinyl group, an allyl group, a methallyl group, a styryl group, anacryloyl group, a meth(acryloyl) group, and a maleimide group. Thesurface treatment agent includes a silane coupling agent having apolymerizable unsaturated bond, for example.

The inorganic filler as Component (B) contributes to improving thedielectric properties, heat resistance, flame retardant properties, andtoughness of the cured product and reducing the thermal expansioncoefficient thereof. In addition, since the inorganic filler asComponent (B) has been subjected to a surface treatment using a surfacetreatment agent, the inorganic filler has polymerizable unsaturatedbonds on the surface thereof. That is why when the Composition (X) iscured, the polymerizable unsaturated bond of the inorganic filler asComponent (B) and the ethylene-propylene-diene copolymer as Component(A) may react to each other, thus causing an increase in the crosslinkdensity of the cured product. This allows the inorganic filler asComponent (B) to contribute to improving the heat resistance of thecured product particularly effectively.

The content of the inorganic filler as Component (B) suitably fallswithin a range from 30 parts by mass to 500 parts by mass relative to100 parts by mass of an organic component having thermosettingproperties of the Composition (X) (hereinafter simply referred to as“thermosetting components”). As used herein, the “content of theinorganic filler as Component (B)” refers to the content of theinorganic filler as Component (B) that has already been subjected to thesurface treatment using a surface treatment agent with polymerizableunsaturated bonds, i.e., the content of the inorganic filler asComponent (B) including the surface treatment agent. Meanwhile, thethermosetting component refers herein to a component that polymerizeswhile the Composition (X) is heated to turn into a cured product. Thethermosetting component includes the ethylene-propylene-diene copolymeras Component (A). When the Composition (X) includes the organic compoundas Component (C), the thermosetting component naturally includes theorganic compound as Component (C). Nevertheless, the surface treatmentagent of the inorganic filler as Component (B) is not counted among thethermosetting components. If the content of the inorganic filler asComponent (B) is equal to or greater than 30 parts by mass, theinorganic filler as Component (B) contributes even more effectively toimproving the heat resistance of the cured product. The content of theinorganic filler as Component (B) is more suitably equal to or greaterthan 50 parts by mass. The content of the inorganic filler as Component(B) is also suitably equal to or greater than 100 parts by mass. In thatcase, the inorganic filler as Component (B) contributes particularlyeffectively to reducing the linear expansion coefficient of the curedproduct. Also, if the content of the inorganic filler as Component (B)is equal to or less than 500 parts by mass, the relative dielectricconstant of the cured product may be kept particularly low. The contentof the inorganic filler as Component (B) is more suitably equal to orless than 350 parts by mass, and even more suitably equal to or lessthan 250 parts by mass.

Optionally, the Composition (X) may contain a thermo-radicalpolymerization initiator. The thermo-radical polymerization initiator isable to promote the curing of the Composition (X) when the thermosettingcomposition is heated. Note that if the thermosetting component in theComposition (X) contains a component that readily produces an activatespecies when heated, then the Composition (X) may contain nothermo-radical polymerization initiators.

The thermo-radical polymerization initiator suitably contains an organicperoxide. The thermo-radical polymerization initiator may contain atleast one component selected from the group consisting of: α, α′-bis(t-butylperoxy-m-isopropyl) benzene;2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne; benzoyl peroxide;3,3′,5,5′-tetramethyl-1,4-diphenoquinone; chloranil;2,4,6-tri-t-butylphenoxyl; t-butylperoxyisopropyl monocarbonate; andazo-bisisobutyronitrile.

The content of the thermo-radical polymerization initiator may, but doesnot have to, fall within a range from 0.1 parts by mass to 3 parts bymass relative to 100 parts by mass of the entire thermosettingcomponents in the Composition (X), for example.

Optionally, the Composition (X) may further contain any additive otherthan the components described above. The additive may include, forexample, at least one component selected from the group consisting of:antifoaming agents such as silicone antifoaming agents and acrylic acidester antifoaming agents; thermal stabilizers; antistatic agents;ultraviolet light absorbers; dyes; pigments; lubricants; and dispersingagents such as wetting and dispersing agents.

The Composition (X) may further contain a solvent as Component (D) asneeded. The solvent as Component (D) suitably contains at least onecomponent selected from the group consisting of: aliphatic hydrocarbonbased solvents; aromatic hydrocarbon based solvents; and ketone basedsolvents. The Composition (X) containing a solvent improves theformability when the Composition (X) is formed into a sheet shape.

3. Resin Sheet

A resin sheet according to this embodiment includes a dried product orsemi-cured product of the Composition (X). The resin sheet may be usedas a material for making a laminate and a printed wiring board. That isto say, the resin sheet may be used to make a laminate with aninsulating layer including a cured product of the resin sheet (i.e., aninsulating layer including a cured product of the Composition (X)) and aprinted wiring board with an insulating layer including a cured productof the resin sheet (i.e., an insulating layer including a cured productof the Composition (X)). Optionally, the resin sheet may also be used asa bonding sheet.

To make a resin sheet, the Composition (X) may be formed into a sheetshape by an application method, for example, and then heated to be driedor semi-cured. In this manner, a resin sheet including a dried productor semi-cured product of the Composition (X) is obtained. The heatingtemperature may fall within the range from 100° C. to 160° C., forexample, and the heating duration may fall within the range from 5minutes to 10 minutes, for example.

Heating and curing the resin sheet allows an insulating layer includinga cured product of the Composition (X) to be formed. The heatingtemperature may fall within the range from 160° C. to 200° C., forexample, and is suitably from 180° C. to 200° C., and the heatingduration may fall within the range from 30 minutes to 120 minutes, forexample, and is suitably from 60 minutes to 120 minutes.

When the resin sheet is used as a bonding sheet, two base members may bebonded together with the resin sheet, for example. Each of the two basemembers may be a laminate or a printed wiring board, for example.Specifically, the Composition (X) may be applied onto a supporting film,for example, and formed into a sheet shape, and then heated to be driedor semi-cured, thus making a resin sheet. This resin sheet is laid ontop of a base member (first base member) and then the supporting film ispeeled from the resin sheet. Subsequently, another base member (secondbase member) is laid on top of the resin sheet. That is to say, thefirst base member, the resin sheet, and the second base member arestacked one on top of another in this order. Subsequently, the resinsheet is heated to be cured. This allows the first base member and thesecond base member to be bonded together via a cured product of theresin sheet.

4. Sheet of Metal Foil With Resin

A sheet of metal foil 1 with resin according to this embodiment includesa sheet of metal foil 10 and a resin layer 20 laid on top of the sheetof metal foil 10. The resin layer 20 includes a dried product orsemi-cured product of the Composition (X).

The sheet of metal foil 10 may be a sheet of copper foil, for example.The sheet of metal foil 10 may have a thickness falling within the rangefrom 2 μm to 105 μm, for example, and is suitably from 5 μm to 35 μm.

The resin layer 20 suitably includes a first resin layer 21 laid on topof the sheet of metal foil 10 and a second resin layer 22 laid on top ofthe first resin layer 21 as shown in FIGS. 1A and 1B. The first resinlayer 21 includes at least one component selected from the groupconsisting of: a liquid crystal polymer resin; a polyimide resin; apolyamide imide resin; a fluorocarbon resin; and a polyphenylene etherresin. The second resin layer 22 includes a dried product or semi-curedproduct of the Composition (X). The first resin layer 21 may have athickness falling within the range from 1 μm to 50 μm, for example. Thesecond resin layer 22 may have a thickness falling within the range from5 μm to 200 μm, and suitably has a thickness falling within the rangefrom 10 μm to 150 μm.

In particular, it is recommended that the thickness of the first resinlayer 21 fall within the range from 1 μm to 50 μm and the thickness ofthe second resin layer 22 fall within the range from 5 μm to 200 μm. Inthis case, setting the thickness of the first resin layer 21 at 1 μm ormore increases the chances of an insulating layer made of the resinlayer 20 exhibiting good electrical insulation properties. Meanwhile,setting the thickness of the first resin layer 21 at 50 μm or lessincreases the chances of the insulating layer made of the resin layer 20having a sufficiently low dielectric constant and a sufficiently lowdielectric loss tangent. Setting the thickness of the second resin layer22 at 5 μm or more further increases the chances of the insulating layermade of the resin layer 20 having a sufficiently low dielectric constantand a sufficiently low dielectric loss tangent. Setting the thickness ofthe second resin layer 22 at 200 μm or less allows the insulating layermade of the resin layer 20 to exhibit sufficient flexibility.

A laminate or a printed wiring board, for example, may be made of thesheet of metal foil 1 with resin. In that case, an insulating layer maybe made of the resin layer 20 of the sheet of metal foil 1 with resin,thus allowing the insulating layer to have a sufficiently low dielectricconstant and a sufficiently low dielectric loss tangent. Particularlywhen the resin layer 20 includes the first resin layer 21 and the secondresin layer 22, the insulating layer made up of the first resin layer 21and the second resin layer 22 is allowed to have a sufficiently lowdielectric constant and a sufficiently low dielectric loss tangent. Inaddition, the first resin layer 21 is further allowed to have goodflexibility and there are slim chances that the cured product of thesecond resin layer 22 interferes with the flexibility of the first resinlayer 21. This allows a flexible metal-clad laminate or printed wiringboard to be formed using the sheet of metal foil 1 with resin.

The first resin layer 21 may be configured as a single layer as shown inFIG. 1A or may include a first layer 211 and a second layer 212 withmutually different compositions as shown in FIG. 1B. When the firstresin layer 21 includes the first layer 211 and the second layer 212,each of the first layer 211 and second layer 212 includes at least onecomponent selected from the group consisting of: a liquid crystalpolymer resin; a polyimide resin; a polyamide imide resin; afluorocarbon resin; and a polyphenylene ether resin, and the secondlayer 212 has a different composition from the first layer 211.

When the sheet of metal foil 1 with resin is made, the first resin layer21 is made from a resin solution containing a material resin or a sheetmaterial containing the material resin. Optionally, the sheet materialmay include, as an internal member, a base member such as glass clothand may be reinforced with the base member. The sheet material may be aprepreg, for example. The first resin layer 21 may be formed by, forexample, providing the sheet of metal foil 10 first, applying a resinsolution onto the sheet of metal foil 10, and then drying the resinsolution. Alternatively, the first resin layer 21 may also be formed bylaying the sheet materials on top of the sheet of metal foil 10 and thenthermally pressing the sheet materials together.

If the first resin layer 21 contains a liquid crystal polymer resin,then the liquid crystal polymer resin may contain at least one componentselected from the group consisting of: polycondensates of ethyleneterephthalate and para-hydroxybenzoic acid; polycondensates of a phenol,phthalic acid, and para-hydroxybenzoic acid; and polycondensates of2,6-hydroxynaphthoic acid and para-hydroxybenzoic acid. The first resinlayer 21 may be formed by forming the liquid crystal polymer resin intoa sheet shape, for example, to make a sheet material and then laying thesheet material on top of the sheet of metal foil.

If the first resin layer 21 contains a polyimide resin, then a resinsolution containing the polyimide resin may be prepared in the followingmanner, for example. First, polyamide acid is produced bypolycondensation of tetracarboxylic dianhydride and a diamine component.The tetracarboxylic dianhydride suitably contains 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride. The diamine component suitablyincludes a component selected from the group consisting of: 2,2-bis[4-(4-aminophenoxy) phenyl] propane; 4,4′-diaminodiphenyl ether; and bis[4-(4-aminophenoxy) phenyl] sulfone. Subsequently, the polyamide acid isheated in a solvent. The solvent contains at least one componentselected from the group consisting of: N-methyl-2-pyrrolidone; methylethyl ketone; toluene; dimethyl acetamide; dimethylformamide; andmethoxypropanol. In this heating process, the heating temperature mayfall within the range from 60° C. to 250° C., and suitably falls withinthe range from 100° C. to 200° C. The heating duration may fall withinthe range from 0.5 hours to 50 hours. This causes the polyamide acid toturn into an imide through cyclization reaction, thus producing apolyimide resin. In this manner, a resin solution containing thepolyimide resin is obtained.

The first resin layer 21 may be formed by applying the resin solutioncontaining the polyimide resin onto the sheet of metal foil 10 and thenheating and drying the resin solution.

If the first resin layer 21 contains a polyamide imide resin, then aresin solution containing the polyamide imide resin may be prepared inthe following manner, for example. First, trimellitic anhydride,4,4′-diisocyanato-3,3′-dimethylbiphenyl, tolylene-2,4-diisocyanate,diazabicycloundecene, and N,N-dimethylacetamide are mixed together toprepare a mixture. The mixture is then heated and the respectivecomponents are allowed to react to each other to obtain a mixturecontaining polyamide imide. Subsequently, the mixture is cooled. Then,bismaleimide is added to this mixture. In this manner, a resin solutioncontaining polyamide imide is obtained.

The first resin layer 21 may be formed by, for example, applying theresin solution containing the polyamide imide resin onto the sheet ofmetal foil 10 and then heating and drying the resin solution.

If the first resin layer 21 contains a fluorocarbon resin, then thefluorocarbon resin may include polytetrafluoroethylene, for example.

If the first resin layer 21 contains a polyphenylene ether resin, thenthe first resin layer 21 is made of a resin composition containing apolyphenylene ether resin having a substituent group havingcarbon-carbon double bonds at terminals and a crosslink agent havingcarbon-carbon double bonds. The crosslink agent includes at least onecomponent selected from the group consisting of: divinylbenzene;polybutadiene; alkyl (meth)acrylate; tricyclodecanol (meth)acrylate;fluorene (meth)acrylate; isocyanurate (meth)acrylate; andtrimethylolpropane (meth)acrylate. The ratio by mass of thepolyphenylene ether resin to the total of the polyphenylene ether resinand the crosslink agent may fall within the range from 65% by mass to95% by mass.

The first resin layer 21 may be formed by, for example, applying theresin solution containing the polyphenylene ether resin and thecrosslink agent having carbon-carbon double bonds onto the sheet ofmetal foil 10 and then thermally curing the resin solution.

If the first resin layer 21 includes the first layer 211 and the secondlayer 212, then the first resin layer 21 may be obtained by, forexample, forming the first layer 211 and the second layer 212 in thisorder onto the sheet of metal foil 10 in the same way as describedabove. For example, first, a resin solution containing the component ofthe first layer 211 is applied onto the sheet of metal foil 10 and thendried to form the first layer 211. Next, a resin solution containing thecomponent of the second layer 212 is applied onto the first layer 211and then dried to form the second layer 212. Alternatively, the firstresin layer 21 may also be formed by stacking a sheet materialcontaining the component of the first layer 211 and a sheet materialcontaining the component of the second layer 212 in this order on thesheet of metal foil 10 and then thermally pressing these sheet materialstogether.

The second resin layer 22 may be formed by, for example, forming thefirst resin layer 21 and applying the Composition (X) onto the firstresin layer 21 and then heating, and drying or semi-curing, theComposition (X). Alternatively, the second resin layer 22 may also beformed by, for example, laying a resin sheet including a dried orsemi-cured product of the Composition (X) that has been described for“3. Resin sheet” on top of the first resin layer 21. The second resinlayer 22 may be formed by subjecting the Composition (X) to a heatingprocess under the condition including a heating temperature fallingwithin the range from 100° C. to 160° C. and a heating duration fallingwithin the range from 5 minutes to 10 minutes, for example. In thismanner, a sheet of metal foil 10 with resin is obtained.

Optionally, the first resin layer 21 may include three or more layers.For example, the first resin layer 21 may include a first layer, asecond layer, and a third layer, which may be stacked one on top ofanother in this order. In that case, each of the first, second, andthird layers contains at least one component selected from the groupconsisting of: a liquid crystal polymer resin; a polyimide resin; apolyamide imide resin; a fluorocarbon resin; and a polyphenylene etherresin. The second layer has a different composition from the firstlayer. The third layer has a different composition from the secondlayer. The third layer may have either a different composition from, orthe same composition as, the first layer.

The resin layer 20 may also be a single layer including a dried productor semi-cured product of the Composition (X). In that case, the resinlayer 20 may be formed by, for example, forming the Composition (X) intoa sheet shape by application method, for example, onto the sheet ofmetal foil 10 and then heating, and drying or semi-curing, theComposition (X). In the heating process, the heating temperature mayfall within the range from 100° C. to 160° C. and the heating durationmay fall within the range from 5 minutes to 10 minutes.

5. Metal-Clad Laminate

A metal-clad laminate 2 according to this exemplary embodiment will bedescribed.

As shown in FIGS. 2A-2D, the metal-clad laminate 2 includes aninsulating layer 30 and the sheet of metal foil 10. The metal-cladlaminate 2 includes the sheet of metal foil 10 as its outermost layer.The insulating layer 30 includes a cured product of the Composition (X).The insulating layer 30 suitably contains at least one componentselected from the group consisting of: a liquid crystal polymer resin; apolyimide resin; a polyamide imide resin; a fluorocarbon resin; and apolyphenylene ether resin.

The metal-clad laminate 2 may include two or more insulating layers 30as shown in FIGS. 2C and 2D. In that case, at least one of the two ormore insulating layers 30 may include a cured product of the Composition(X). Also, at least one of the two or more insulating layers 30 suitablycontains at least one component selected from the group consisting of: aliquid crystal polymer resin; a polyimide resin; a polyamide imideresin; a fluorocarbon resin; and a polyphenylene ether resin. Moresuitably, each of the two or more insulating layers 30 contains at leastone component selected from the group consisting of: a liquid crystalpolymer resin; a polyimide resin; a polyamide imide resin; afluorocarbon resin; and a polyphenylene ether resin.

The sheet of metal foil 10 may be a sheet of copper foil, for example.The sheet of metal foil 10 may have a thickness falling within the rangefrom 2 μm to 105 μm, for example.

The insulating layers 30 may include a first layer 301 and a secondlayer 302 laid on top of the first layer 301. The first layer 301contains at least one component selected from the group consisting of: aliquid crystal polymer resin; a polyimide resin; a polyamide imideresin; a fluorocarbon resin; and a polyphenylene ether resin. The secondlayer 302 includes a cured product of the Composition (X). Thus, theinsulating layers 30 include the cured product of the Composition (X).The first layer 301 may have a thickness falling within the range from 1μm to 50 μm, for example, and the second layer 302 may have a thicknessfalling within the range from 5 μm to 50 μm, for example. Optionally,the insulating layers 30 may also be configured as a single layerincluding a cured product of the Composition (X).

The metal-clad laminate 2, provided with the insulating layers 30including the cured product of the Composition (X), allows theinsulating layers 30 to have a sufficiently low dielectric constant anda sufficiently low dielectric loss tangent. This also allows theinsulating layers 30 to have high heat resistance. In addition, sincethe cured product of the Composition (X) has good adhesiveness to resinsand metals, the insulating layers 30 and the layers in contact with theinsulating layers 30 may keep sufficiently close contact with eachother.

The metal-clad laminate 2, provided with the first layer 301 and thesecond layer 302 described above as the insulating layers 30, allows theinsulating layers 30 to have an even lower dielectric constant and aneven lower dielectric loss tangent. This also allows the insulatinglayers 30 to have high heat resistance. In addition, since the curedproduct of the Composition (X) has good adhesiveness to resins andmetals, the second layer 302 and the layers in contact with the secondlayer 302 may keep sufficiently close contact with each other.

The metal-clad laminates 2 shown in FIGS. 2A-2D will be described infurther detail.

The metal-clad laminate 2 shown in FIG. 2A includes the sheet of metalfoil 10, the first layer 301, and the second layer 302, which arestacked one on top of another in this order.

To manufacture the metal-clad laminate 2 shown in FIG. 2A, the firstlayer 301 may be formed by, for example, applying a resin solutioncontaining the component of the first layer 301 onto the sheet of metalfoil 10 and then drying the resin solution. Alternatively, the firstlayer 301 may also be formed by laying a sheet material containing thecomponent of the first layer 301 on top of the sheet of metal foil 10and then thermally pressing the sheet material.

Next, the second layer 302 may be formed by applying the Composition (X)onto the first layer 301, heating, and thereby drying or semi-curing,the Composition (X) under the condition including a heating temperaturefalling within the range from 100° C. to 160° C. and a heating durationfalling within the range from 5 minutes to 10 minutes, and then furtherheating, and thereby curing, the Composition (X) under the conditionincluding a heating temperature falling within the range from 160° C. to200° C. and a heating duration falling within the range from 30 minutesto 120 minutes. In this manner, the metal-clad laminate 2 may be made.

Alternatively, the metal-clad laminate 2 may also be formed by stackinga sheet material containing the component of the first layer 301 and aresin sheet including a dried product or semi-cured product of theComposition (X) that has already been described for the “3. Resin sheet”section one on top of the other in this order on the sheet of metal foil10 and then thermally pressing the sheet material and the resin sheettogether.

Still alternatively, the metal-clad laminate 2 may also be made byheating the sheet of metal foil 1 with resin shown in FIG. 1A andthereby curing the second resin layer 22.

Optionally, in the metal-clad laminate 2 shown in FIG. 2A, the sheet ofmetal foil 10, the second layer 302, and the first layer 301 may bestacked one on top of another in this order. That is to say, the firstlayer 301 and the second layer 302 may be stacked in reverse order fromthe example illustrated in FIG. 2A. Furthermore, the first layer 301 mayinclude two or more layers. In that case, two layers that are directlyin contact with each other in the first layer 301 have mutuallydifferent compositions. Meanwhile, two layers that are not directly incontact with each other in the first layer 301 may have either the samecomposition or mutually different compositions.

Next, the metal-clad laminate 2 shown in FIG. 2B will be described. Thismetal-clad laminate 2 includes a sheet of metal foil 10 (first sheet ofmetal foil 11), the insulating layers 30, and another sheet of metalfoil 10 (second sheet of metal foil 12), which are stacked one on top ofanother in this order. That is to say, the metal-clad laminate 2 shownin FIG. 2B has the same configuration as the metal-clad laminate 2 shownin FIG. 2A except that the metal-clad laminate 2 shown in FIG. 2Bfurther includes the second sheet of metal foil 12.

The metal-clad laminate 2 shown in FIG. 2B may be formed by stacking thefirst sheet of metal foil 11, a sheet material containing the componentof the first layer 301, a sheet material containing the component of thesecond layer 302, and the second sheet of metal foil 12 one on top ofanother in this order and then thermally pressing these memberstogether.

Alternatively, the metal-clad laminate 2 may also be made by laying asheet of metal foil on top of the second resin layer 22 of the sheet ofmetal foil 1 with resin shown in FIG. 1A and then thermally pressingthem together. Optionally, the metal-clad laminate 2 shown in FIG. 2Amay be obtained by completely etching away the second sheet of metalfoil 12 from the metal-clad laminate 2 shown in FIG. 2B.

Another metal-clad laminate 2 according to this embodiment may includethe sheet of metal foil 10, insulating layers 30 (first insulating layer31), a conductor layer 50, and another insulating layer 30 (secondinsulating layer 32), which are stacked one on top of another in thisorder as shown in FIGS. 2C and 2D. In that case, the second insulatinglayer 32 suitably contains at least one component selected from thegroup consisting of: a liquid crystal polymer resin; a polyimide resin;a polyamide imide resin; a fluorocarbon resin; and a polyphenylene etherresin.

In the metal-clad laminate 2 shown in FIG. 2C, the first insulatinglayer 31 includes the first layer 301 and the second layer 302. Thefirst insulating layer 31 may have the same configuration as theinsulating layers 30 of the metal-clad laminate 2 shown in FIG. 2A. Theconductor layer 50 may be either a sheet of metal foil or conductorwiring.

The metal-clad laminate 2 shown in FIG. 2C may be made by, for example,stacking the sheet of metal foil 10, a sheet material containing thecomponent of the first layer 301, another sheet material containing thecomponent of the second layer 302, the conductor layer 50, and stillanother sheet material containing the component of the second insulatinglayer 32 one on top of another in this order and then thermally pressingthese members together.

Alternatively, the metal-clad laminate 2 shown in FIG. 2C may be formedof the sheet of metal foil 1 with resin shown in FIG. 1A and a basemember including the conductor layer 50 and the second insulating layer32. The conductor layer 50 is configured as either a sheet of metal foilor conductor wiring. For example, the metal-clad laminate 2 may be madeby laying the conductor layer 50 of the base member on top of the secondresin layer 22 of the sheet of metal foil 1 with resin and thenthermally pressing them together.

Alternatively, the metal-clad laminate 2 may include the sheet of metalfoil 10, the second layer 302, the first layer 301, the conductor layer50, and the second insulating layer 32, which are stacked one on top ofanother in this order. That is to say, the first layer 301 and thesecond layer 302 may be stacked one upon the other in reverse order fromthe example shown in FIG. 2C.

The metal-clad laminate shown in FIG. 2D includes a sheet of metal foil10 (first sheet of metal foil 11), the insulating layers 30 (firstinsulating layer 31), the conductor layer 50, the insulating layer 30(second insulating layer 32), and another sheet of metal foil 10 (secondsheet of metal foil 12), which are stacked one on top of another in thisorder. The first insulating layer 31 includes the first layer 301 andthe second layer 302. That is to say, the metal-clad laminate 2 shown inFIG. 2D has the same configuration as the metal-clad laminate 2 shown inFIG. 2C except that the metal-clad laminate 2 shown in FIG. 2D furtherincludes the second sheet of metal foil 12.

The metal-clad laminate 2 shown in FIG. 2D may be made by stacking thefirst sheet of metal foil 11, a sheet material containing the componentof the first layer 301, another sheet material containing the componentof the second layer 302, the conductor layer 50 as a sheet of metalfoil, still another sheet material containing the component of thesecond insulating layer, and the second sheet of metal foil 12 one ontop of another in this order and then thermally pressing these memberstogether.

Alternatively, the metal-clad laminate 2 shown in FIG. 2D may also beformed of the sheet of metal foil 1 with resin shown in FIG. 1A and abase member including the conductor layer 50, the second insulatinglayer 32, and the second sheet of metal foil 12 that are stacked one ontop of another in this order. The conductor layer 50 may be configuredas either a sheet of metal foil or conductor wiring. The metal-cladlaminate 2 may be made by laying the conductor layer 50 of the basemember on top of the second resin layer 22 of the sheet of metal foil 1with resin and then thermally pressing them together.

Optionally, the metal-clad laminate 2 may also be formed by usingappropriate materials selected from the group consisting of a sheet ofmetal foil with resin, a single-sided metal-clad laminate, adouble-sided metal-clad laminate, a sheet material, and a sheet of metalfoil. For example, a base member including the first sheet of metal foil11 and the first layer 301 laid on top of the first sheet of metal foil11 (hereinafter referred to as a “first base member”) is provided. Inthe meantime, a base member including the conductor layer 50 configuredas a sheet of metal foil or conductor wiring, the second insulatinglayer 32, and the second sheet of metal foil 12, which are laid one ontop of another in this order (hereinafter referred to as a “second basemember”) is also provided. The first layer 301 of the first base memberand the conductor layer 50 of the second base member are arranged toface each other, the resin sheet described for “3. Resin sheet” sectionis interposed between these two layers, and then these members arethermally pressed together. This allows the second layer 302 to beformed by curing the resin sheet and the first base member and thesecond base member to be bonded together via the second layer 302, thusforming the metal-clad laminate 2.

Optionally, the metal-clad laminate 2 shown in FIG. 2C may be made bycompletely etching away the second sheet of metal foil 12 from themetal-clad laminate 2 shown in FIG. 2D, for example.

Note that the specific examples shown in FIGS. 2A-2D are only exemplarystructures for the metal-clad laminate 2 and should not be construed aslimiting. For example, the metal-clad laminate 2 may include one or moresheets of metal foil 10, two or more conductor layers 50, and three ormore insulating layers 30. The conductor layer 50 is interposed betweentwo adjacent ones of the insulating layers 30. The sheet of metal foil10 forms the outermost layer of the metal-clad laminate 2. At least oneof the three or more insulating layers 30 includes a cured product ofthe Composition (X). At least one of the three or more insulating layers30 suitably contains at least one component selected from the groupconsisting of: a liquid crystal polymer resin; a polyimide resin; apolyamide imide resin; a fluorocarbon resin; and a polyphenylene etherresin. Particularly when the metal-clad laminate 2 includes aninsulating layer 30 including either a polyimide resin or a polyamideimide resin, or both, the heat resistance and size stability of themetal-clad laminate 2 may further improve.

6. Printed Wiring Board

A printed wiring board 3 according to this embodiment will be described.

As shown in FIGS. 3A-3D, the printed wiring board 3 includes aninsulating layer 30 and conductor wiring 60. The printed wiring board 3includes the conductor wiring 60 as its outermost layer. The insulatinglayer 30 includes a cured product of the Composition (X). The insulatinglayer 30 suitably includes at least one component selected from thegroup consisting of: a liquid crystal polymer resin; a polyimide resin;a polyamide imide resin; a fluorocarbon resin; and a polyphenylene etherresin.

The printed wiring board 3 may include two or more insulating layers 30.In that case, at least one of the two or more insulating layers 30 mayinclude a cured product of the Composition (X). Also, at least one ofthe two or more insulating layers 30 suitably includes at least onecomponent selected from the group consisting of: a liquid crystalpolymer resin; a polyimide resin; a polyamide imide resin; afluorocarbon resin; and a polyphenylene ether resin. More suitably, eachof the two or more insulating layers 30 includes at least one componentselected from the group consisting of: a liquid crystal polymer resin; apolyimide resin; a polyamide imide resin; a fluorocarbon resin; and apolyphenylene ether resin.

The conductor wiring 60 may have a thickness falling within the rangefrom 2 μm to 105 μm, for example. Examples of the conductor wiring 60include a signal layer, a power supply layer, and a ground layer. Theconductor wiring 60 may have an appropriate pattern. On the drawingsattached herewith, the conductor wiring 60 is illustrated as asimplified one. Optionally, the insulating layer 30 may have a viametal.

The insulating layer 30 may include a first layer 301 and a second layer302 laid on top of the first layer 301. The insulating layer 30 may havethe same configuration as the insulating layer 30 of the metal-cladlaminate 2 shown in any of FIGS. 2A-2D.

The printed wiring board 3 achieves the same advantages as themetal-clad laminate 2.

The printed wiring boards 3 shown in FIGS. 3A-3D will be described infurther detail.

The printed wiring board 3 shown in FIG. 3A includes the conductorwiring 60, the first layer 301, and the second layer 302, which arestacked one on top of another in this order. The printed wiring board 3has the same configuration as the metal-clad laminate 2 shown in FIG.2A, except that the printed wiring board 3 includes the conductor wiring60 in place of the sheet of metal foil 10. This printed wiring board 3may be made by forming the conductor wiring 60 by, for example, etchingaway excessive portions of the sheet of metal foil 10 of the metal-cladlaminate 2 shown in FIG. 2A.

The printed wiring board 3 shown in FIG. 3B includes the conductorwiring 60, the insulating layer 30, and a conductor layer 50, which arestacked one on top of another in this order. That is to say, the printedwiring board 3 shown in FIG. 3B has the same configuration as theprinted wiring board 3 shown in FIG. 3A, except that the printed wiringboard 3 shown in FIG. 3B further includes the conductor layer 50. Theconductor layer 50 may be a sheet of metal foil or conductor wiring,whichever is appropriate. This printed wiring board 3 may be made byforming the conductor wiring 60 by, for example, etching away excessiveportions of the first sheet of metal foil 11 of the metal-clad laminate2 shown in FIG. 2B and/or by forming another conductor wiring by etchingaway excessive portions of the second sheet of metal foil 12 as well.

Each of the printed wiring boards 3 shown in FIGS. 3C and 3D is amultilayer printed wiring board 4 including one or more conductorwirings 60 and two or more insulating layers 30. The multilayer printedwiring board 4 may be made using the sheet of metal foil with resin,laminate, or printed wiring board described above, for example.

The multilayer printed wiring board 4 shown in FIG. 3C includes theconductor wiring 60, an insulating layer 30 (first insulating layer 31),the conductor layer 50, and another insulating layer 30 (secondinsulating layer 32), which are stacked one on top of another in thisorder. The conductor layer 50 is configured as either a sheet of metalfoil or conductor wiring. The insulating layer 30 includes a first layer301 and a second layer 302. This multilayer printed wiring board 4 hasthe same configuration as the printed wiring board 3 shown in FIG. 3Bexcept that the multilayer printed wiring board 4 further includes thesecond insulating layer 32 and has the same configuration as themetal-clad laminate 2 shown in FIG. 2C except that the multilayerprinted wiring board 4 includes the conductor wiring 60 in place of thesheet of metal foil 10.

The multilayer printed wiring board 4 shown in FIG. 3C may be made byforming the conductor wiring 60 by, for example, etching away excessiveportions of the sheet of metal foil 10 of the metal-clad laminate 2shown in FIG. 2C.

The multilayer printed wiring board 4 shown in FIG. 3D includes theconductor wiring 60, an insulating layer 30 (first insulating layer 31),a conductor layer 50 (first conductor layer 51), another insulatinglayer 30 (second insulating layer 32), and another conductor layer 50(second conductor layer 52), which are stacked one on top of another inthis order. That is to say, the multilayer printed wiring board 4 shownin FIG. 3D has the same configuration as the multilayer printed wiringboard 4 shown in FIG. 3C except that the multilayer printed wiring board4 shown in FIG. 3D further includes the second conductor layer 52. Eachof the first conductor layer 51 and the second conductor layer 52 may beconfigured as either a sheet of metal foil or conductor wiring,whichever is appropriate.

The multilayer printed wiring board 4 shown in FIG. 3D may be formed outof either the sheet of metal foil 1 with resin or the metal-cladlaminate 2, for example. The multilayer printed wiring board 4 may bemade by forming the conductor wiring 60 by, for example, etching awayexcessive portions of the first sheet of metal foil 11 of the metal-cladlaminate 2 shown in FIG. 2D and/or forming another conductor wiring by,for example, etching away excessive portions of the second sheet ofmetal foil 12 thereof.

Note that the specific examples shown in FIGS. 3C and 3D illustrate onlyexemplary configurations for the multilayer printed wiring boards 4 andshould not be construed as limiting. For example, the multilayer printedwiring board 4 may include three or more insulating layers 30.

EXAMPLES

Specific examples of the present disclosure will be presented below.Note that the following specific examples are only examples of thepresent disclosure and should not be construed as limiting.

1. Making Resin Sheet

A composition with a solid content concentration of 25% by mass wasobtained by adding the components shown in the “Composition” column ofTables 1 and 2 to toluene.

Using a comma coater and a drier connected to the comma coater, thecomposition was applied onto a polyethylene terephthalate film with athickness of 38 μm, and then heated at 110° C. for 5 minutes. In thismanner, a resin sheet with a thickness of 25 μm was formed on thepolyethylene terephthalate film.

Among the components shown in the “Material Composition” column ofTables 1 and 2, details of all components but the vinyl compound havinga polyphenylene either skeleton are as follows:

-   -   Copolymer 1: ethylene-propylene-diene copolymer having a Mooney        viscosity (ML (1+4) 100° C.) of 15, an ethylene content of 72%        by mass, and a diene content of 3.6% by mass, and a product        number X-3012P manufactured by Mitsui Chemicals Inc.;    -   Copolymer 2: ethylene-propylene-diene copolymer having a Mooney        viscosity (ML (1+4) 100° C.) of 32, an ethylene content of 47%        by mass, and a diene (5-ethylidene-2-norbornene) content of 9.5%        by mass, and a product number 8030M manufactured by Mitsui        Chemicals Inc.;    -   Copolymer 3: ethylene-propylene-diene copolymer having a Mooney        viscosity (ML (1+4) 125° C.) of 58, an ethylene content of 41%        by mass, and a diene (5-ethylidene-2-norbornene) content of        14.0% by mass, and the product number 9090M manufactured by        Mitsui Chemicals Inc.;    -   Organic Compound 1 having a polymerizable unsaturated group: the        compound expressed by Formula (2) and having the product number        DD-1 manufactured by Shikoku Chemicals Corporation;    -   Organic Compound 2 having a polymerizable unsaturated group:        divinylbenzene manufactured by Tokyo Chemical Industry Co.,        Ltd.;    -   Organic Compound 3 having a polymerizable unsaturated group:        tricyclodecane dimethanol dimethacrylate having the product        number DCP manufactured by Shin-Nakamura Chemical Co., Ltd.;    -   Organic Compound 4 having a polymerizable unsaturated group:        long-chain alkylbismaleimide having the product number BMI-689        manufactured by Molecular Design Inc.;    -   Bismaleimide: product number BMI-1000 manufactured by Daiwa Fine        Chemicals Co., Ltd.;    -   Epoxy compound: product number NC-300011 manufactured by Nippon        Kayaku Co., Ltd.;    -   Elastomer 1: product name SEPTON™ V9827 manufactured by Kuraray        Co., Ltd.;    -   Elastomer 2: product name HYBRAR™ 7125 manufactured by Kuraray        Co., Ltd.;    -   Elastomer 3: product name HYBRAR™ 5127 manufactured by Kuraray        Co., Ltd.;    -   Inorganic Filler 1: spherical silica surface-treated with vinyl        silane and having the product number 0.5 μm SV-CTI (25% toluene        containing slurry) manufactured by Admatechs;    -   Inorganic Filler 2: spherical silica surface-treated with        methacrylic silane and having the product number 0.5 μm SM-CTI.        (25% toluene containing slurry) manufactured by Admatechs;    -   Inorganic Filler 3: spherical silica surface-treated with phenyl        silane and having the product number 0.5 μm SP-CTI (25% toluene        containing slurry) manufactured by Admatechs; and    -   Thermo-Radical Polymerization Initiator: product name Perbutyl P        manufactured by NOF Corporation.

Meanwhile, the vinyl compound having a polyphenylene ether skeleton wassynthesized in the following manner. Into a three-neck flask having acapacity of 1 liter and provided with a temperature adjuster, a stirrer,a cooling system, and a dripping funnel, 200 g of polyphenylene ether(product number SA90 manufactured by SABIC Innovative Plastic, having anintrinsic viscosity of 0.083 dl/g, an average number of terminalhydroxyl groups of 1.9, and a number average molecular weight of 2,000),30 g of 50:50 by mass mixture of p-chloromethylstyrene andm-chloromethylstyrene (product name chloromethylstyrene: CMSmanufactured by Tokyo Chemical Industry Co., Ltd.), 1.227 g ofphase-transfer catalyst (tetra-n-butyl ammonium bromide), and 400 g oftoluene were introduced. The mixture of these components was graduallyheated to 75° C. while being stirred up. Next, an aqueous solution of analkali metal hydroxide (i.e., a mixture of 20 g of sodium hydroxide and29 g of water) was dripped in 20 minutes into the three-neck flask.Subsequently, the content of the three-neck flask was stirred up at 75°C. for four hours. Thereafter, the content of the three-neck flask wasneutralized with 10% by mass of hydrochloric acid, and then a lot ofmethanol was poured into the three-neck flask, thereby depositing theprecipitate. The precipitate was separated by filtering the content ofthe three-neck flask. Thereafter, the precipitate was washed three timeswith a 80:20 by mass mixture of methanol and water, and then dried at80° C. for three hours at a reduced pressure, thereby obtaining aproduct. When the product was analyzed with 1H-NMR (400 MHz, CDC13,TMS), a peak derived from ethenylbenzyl was confirmed within the rangeof 5 to 7 ppm. Thus, it was confirmed that the product was a vinylcompound with a polyphenylene ether skeleton having, at a terminal, asubstituent group with carbon-carbon double bonds.

2. Evaluation Test

2-1. Dielectric Properties (Relative Dielectric Constant and DielectricLoss Tangent)

Two sheets of copper foil, each having a thickness of 18 μm, werearranged so that the glossy surfaces thereof faced each other, and aresin sheet was interposed between the two sheets of copper foil. Asample was made by thermally pressing them for one hour under thecondition including 200° C. and 2 MPa. This sample was subjected to anetching process to remove the two sheets of copper foil from both sides,thereby making a test piece of a cured product of the resin sheet. Therelative dielectric constant and dielectric loss tangent of this testpiece at a test frequency of 10 GHz were measured in accordance with theIPC TM-650 2.5.5.5. Note that one of the criteria of “low dielectricconstant” according to this embodiment may be that the dielectricconstant according to this test should be equal to or less than 3.0. Itshould also be noted that one of the criteria of “low dielectric losstangent” according to this embodiment may be that the dielectric losstangent according to this test should be equal to or less than 0.0025.

2-2. Peel Strength 1 (Peel Strength With Respect to Resin)

Two base members, each including a sheet of copper foil with a thicknessof 12 μm and an insulating layer of polyamide imide with a thickness of3 μm, were provided. These two base members were arranged so that theirrespective insulating layers faced each other, and a resin sheet wasinterposed between the two insulating layers. A sample was made bythermally pressing them for one hour under the condition including 200°C. and 2 MPa. A 90° peel strength of the cured product of the resinsheet with respect to the insulating layer of polyamide imide of thissample was measured. Note that one of criteria of “high degree ofadhesiveness with respect to resin” according to this embodiment may bethat the peel strength according to this test should be equal to orgreater than 0.5 N/mm.

2-3. Peel Strength 2 (Peel Strength With Respect to Metal)

A base member including a sheet of copper foil with a thickness of 12 μmand an insulating layer of polyamide imide with a thickness of 3 μm, anda sheet of copper foil with a thickness of 12 μm were provided. The basemember and the sheet of copper foil were arranged so that the insulatinglayer of the base member and the sheet of copper foil faced each other,and a resin sheet was interposed between the insulating layer and thesheet of copper foil. A sample was made by thermally pressing them forone hour under the condition including 200° C. and 2 MPa. A 90° peelstrength of the cured product of the resin sheet with respect to thesheet of coper foil of this sample was measured. Note that one ofcriteria of “high degree of adhesiveness with respect to metal”according to this embodiment may be that the peel strength according tothis test should be equal to or greater than 0.5 N/mm.

2-4. Solder Heat Resistance 1

A sample was made in the same way as in the “Peel Strength 1” testdescribed above. A test piece was formed out of the sample in accordancewith the JIS C6471 standard. Specifically, the test piece was liftedafter having been floated on solder baths at 260° C. and 300° C. forthree minutes and then had its appearance observed. When no swelling,peeling, or any other abnormality was observed at a solder bathtemperature of 260° C. or 300° C., the solder heat resistance wasevaluated “A.” When no abnormality was observed at a solder bathtemperature of 260° C. but an abnormality was observed at a solder bathtemperature of 300° C., the solder heat resistance was evaluated “B.”When an abnormality was observed at both of solder bath temperatures of260° C. and 300° C., the solder heat resistance was evaluated “C.” Notethat one of criteria of “high heat resistance” according to thisembodiment may be that the evaluation according to this test should be“A” or “B.”

2-5. Solder Heat Resistance 2

A sample was made in the same way as in the “Peel Strength 2” testdescribed above. A test piece was formed out of the sample in accordancewith the JIS C6471 standard. Specifically, the test piece was liftedafter having been floated on solder baths at 260° C. and 300° C. forthree minutes and then had its appearance observed. When no swelling,peeling, or any other abnormality was observed at a solder bathtemperature of 260° C. or 300° C., the solder heat resistance wasevaluated “A.” When no abnormality was observed at a solder bathtemperature of 260° C. but an abnormality was observed at 300° C., thesolder heat resistance was evaluated “B.” When an abnormality wasobserved at both of 260° C. and 300° C., the solder heat resistance wasevaluated “C.” Note that one of criteria of “high heat resistance”according to this embodiment may be that the evaluation according tothis test should be “A” or “B.”

TABLE 1 Example 1 2 3 4 5 6 7 Composition Copolymer 1 60 60 60 60 60 6060 (parts by mass) Copolymer 2 20 20 20 20 20 20 Copolymer 3 40 Organiccompound 1 20 20 20 20 20 20 with polymerizable unsaturated groupOrganic compound 2 with polymerizable unsaturated group Organic compound3 with polymerizable unsaturated group Organic compound 4 withpolymerizable unsaturated group Vinyl compound with polyphenylene etherskeleton Bismaleimide Epoxy compound Elastomer 1 Elastomer 2 Elastomer 3Inorganic filler 1 50 100 150 250 Inorganic tiller 2 50 250 100Inorganic filler 3 Thermo-radical 3 3 3 3 3 3 3 polymerization initiatorEvaluation Relative dielectric constant 2.25 2.45 2.54 2.7 2.33 2.66 2.4Dielectric loss tangent 0.0018 0.0019 0.0018 0.0019 0.0018 0.0022 0.0009Peel strength 1 (N/mm) 0.5 0.6 0.7 0.6 0.6 0.7 0.6 Peel strength 2(N/mm) 0.7 0.6 0.6 0.5 0.6 0.5 0.8 Solder heat resistance 1 A A A A A AA Solder heat resistance 2 A A A A A A A

TABLE 2 Example 8 9 10 11 12 13 14 Composition Copolymer 1 60 60 60 6060 69 37.5 (parts by mass) Copolymer 2 20 20 20 20 20 22 12.5 Copolymer3 Organic compound 1 20 20 9 50 with polymerizable unsaturated groupOrganic compound 2 20 with polymerizable unsaturated group Organiccompound 3 20 with polymerizable unsaturated group Organic compound 4 20with polymerizable unsaturated group Vinyl compound with polyphenyleneether skeleton Bismaleimide Epoxy compound Elastomer 1 Elastomer 2Elastomer 3 Inorganic filler 1 100 100 100 30 350 100 160 Inorganicfiller 2 Inorganic filler 3 Thermo-radical 3 3 3 3 3 3 4.8polymerization initiator Evaluation Relative dielectric constant 2.352.45 2.34 2.17 2.93 2.31 2.94 Dielectric loss tangent 0.0012 0.00210.0019 0.0014 0.0015 0.0017 0.0019 Peel strength 1 (N/mm) 0.5 0.6 0.60.9 0.5 0.7 0.5 Peel strength 2 (N/mm) 0.6 0.7 0.6 1.2 0.5 0.8 0.6Solder heat resistance 1 A A B A A B A Solder heat resistance 2 A A B AA A A

TABLE 3 Comparative Example 1 2 3 4 5 6 7 8 Composition Copolymer 1 6760 (parts by mass) Copolymer 2 16.5 20 Copolymer 3 Organic compound 116.5 20 20 with polymerizable unsaturated group Organic compound 2 withpolymerizable unsaturated group Organic compound 3 with polymerizableunsaturated group Organic compound 4 with polymerizable unsaturatedgroup Vinyl compound with 12.6 12.6 16 15 15 polyphenylene etherskeleton Bismaleimide 13.7 13.7 5 5 5 Epoxy compound 5.3 5.3 5 5Elastomer 1 68.4 Elastomer 2 68.4 75 75 80 Elastomer 3 79 Inorganicfiller 1 50 100 100 Inorganic filler 2 Inorganic filler 3 100Thermo-radical 3 2 2 3 3 polymerization Initiator Evaluation Relativedielectric constant 2.1 2.3 2.4 2.3 2.5 2.6 2.52 2.5 Dielectric losstangent 0.0011 0.0006 0.0005 0.0002 0.0005 0.0005 0.0002 0.0021 Peelstrength 1 (N/mm) 0.7 0.5 0.5 0.1 1 1.4 0.6 0.8 Peel strength 2 (N/mm)1.2 0.6 0.7 0.1 1.2 1.3 0.8 1 Solder heat resistance 1 C C C C A A C CSolder heat resistance 2 C C C C A A C C

As can be seen from Tables 1, 2, and 3, the thermosetting compositionsof Examples 1 to 10, each containing an ethylene-propylene-dienecopolymer (A) and an inorganic filler (B), have higher solder heatresistance ratings than the thermosetting composition of ComparativeExample 1 containing no inorganic filler (B) and the thermosettingcompositions of Comparative Examples 2 to 4 containing noethylene-propylene-diene copolymer (A) or inorganic filler (B). Inaddition, the thermosetting compositions of Examples 1 to 10 have higherdielectric loss tangent ratings than thermosetting compositions ofComparative Examples 5 and 6 containing no ethylene-propylene-dienecopolymer (A).

In addition, comparing Examples 1 to 6, each containing an inorganicfiller (B) surface-treated with a surface treatment agent having apolymerizable unsaturated bond to Comparative Example 7 containing aninorganic filler surface-treated with a surface treatment agent havingno polymerizable unsaturated bonds instead of the inorganic filler (B),it can be seen that the inorganic filler (B) surface-treated with asurface treatment agent having a polymerizable unsaturated bond doescontribute to improving the solder heat resistance.

Furthermore, comparing Examples 1 to 6, each containing anethylene-propylene-diene copolymer (A), to Comparative Example 8containing no ethylene-propylene-diene copolymers (A), it can be seenthat the ethylene-propylene-diene copolymer (A) does contribute toimproving the solder heat resistance.

These results reveal that the cured product of the thermosettingcomposition, containing the ethylene-propylene-diene copolymer (A) andthe inorganic filler (B) surface-treated with the surface treatmentagent with the polymerizable unsaturated bond, should have a lowerdielectric constant, a lower dielectric loss tangent, higher heatresistance, and a higher degree of adhesiveness with respect to a resin,than known ones.

1. A thermosetting composition comprising: an ethylene-propylene-dienecopolymer as Component (A); and an inorganic filler, as Component (B),surface-treated with a surface treatment agent having a polymerizableunsaturated bond.
 2. The thermosetting composition of claim 1, whereinthe content of the inorganic filler as the Component (B) falls within arange from 30 parts by mass to 500 parts by mass relative to 100 partsby mass of the ethylene-propylene-diene copolymer as the Component (A).3. The thermosetting composition of claim 1, further comprising, asComponent (C), an organic compound having a polymerizable unsaturatedgroup.
 4. The thermosetting composition of claim 3, wherein the contentof the organic compound as the Component (C) falls within a range from 1part by mass to 100 parts by mass relative to 100 parts by mass of theethylene-propylene-diene copolymer as the Component (A).
 5. A resinsheet comprising a dried product or semi-cured product of thethermosetting composition of claim
 1. 6. A sheet of metal foil withresin, comprising: a sheet of metal foil; and a resin layer laid on topof the sheet of metal foil, the resin layer including a dried product orsemi-cured product of the thermosetting composition of claim
 1. 7. Thesheet of metal foil with resin of claim 6, wherein the resin layerincludes: a first resin layer stacked on the sheet of metal foil; and asecond resin layer stacked on the first resin layer, the first resinlayer contains at least one component selected from the group consistingof: a liquid crystal polymer; a polyimide; a polyamide imide; afluorocarbon resin; and polyphenylene ether, and the second resin layerincludes a dried product or semi-cured product of the thermosettingcomposition.
 8. The sheet of metal foil with resin of claim 7, whereinthe first resin layer has a thickness of 1 μm to 50 μm, and the secondresin layer has a thickness of 5 μm to 200 μm.
 9. A metal-clad laminatecomprising: an insulating layer; and a sheet of metal foil, theinsulating layer including a cured product of the thermosettingcomposition of claim
 1. 10. A printed wiring board comprising: aninsulating layer; and conductor wiring, the insulating layer including acured product of the thermosetting composition of claim 1.